Weather is like the path of a single smoke particle above a campfire: reacting in the short-term to small-scale factors, such as the behavior of neighboring particles and tiny differences in micro-temperature and pressure. Climate is like the path of the entire column of smoke: reacting in the long-term to large-scale forces like the prevailing wind and large-scale pressure gradient.

It's much harder to predict the path of a single smoke particle over a few seconds than to predict the path of the entire smoke column over many minutes. This is why we have trouble predicting the weather for two Tuesdays from now, but can model large-scale climate changes over decades.